Previous two stroke engines deliver intake air through the crankcase to the combustion chamber by the pumping action of the piston. Generally, lubricating oil is mixed with the intake air so as to lubricate the crankshaft and piston. The result is increased oil consumption and emissions compared to a conventional four stroke engine. There are two stroke engines with sealed crankcases. However, these have both the intake and exhaust valves in the cylinder head with the result of increased problems of scavenging the products of combustion. The present invention solves the scavenging problem by locating the exhaust valve proximate bottom dead center for lengthwise scavenging and solves the oil consumption problem by sealing the crankcase with a step type piston. The step piston having piston rings located only at a bottommost portion and a body portion defining the rest of the piston wherein it is spaced from the cylinder wall.